Memory Forms at 30 Weeks in the Womb

WEDNESDAY July 15, 2009 -- Fetuses that are only 30 weeks old may already possess short-term memory, Dutch researchers report.

"This is the next step into a better insight in the development of the fetal central nervous system," said study co-author Dr. Jan G. Nijhuis, director of the Centre for Genetics, Reproduction and Child Health at Maastricht University Medical Centre in the Netherlands. "We aim to develop an 'intra-uterine neurologic examination,' which could then be used in fetuses at risk."

Although memory is thought to develop while the baby is still in the womb, little else is known about the phenomenon.

"It is a fairly new idea to look at whether learning occurs in utero," said Dr. Russell Fothergill, an assistant professor of obstetrics and gynecology at Texas A&M Health Science Center College of Medicine and director of ambulatory care at Scott & White.

The authors recruited 93 pregnant Dutch women, and then measured fetal responses to repeated "vibroacoustic" stimulation. Their report appears in the July/August issue of Child Development.

"We used a vibroacoustic stimulator, which leads to a combined stimulus of vibration and sound," Nijhuis explained. "The stimuli were applied to the maternal abdomen above the fetal legs for a period of one second every 30 seconds. We counted the number of stimuli after which the fetus does not respond anymore."

When the fetus makes the change to no longer responding, it is "habituated"; it recognizes the stimulus as "safe."

The authors stated that habituation is a form of learning and needs an intact central nervous system.

"In its simplest form, [habituation] is related to how we think about humans learning," Fothergill said.

According to background information in the paper, the first study to look at fetal habituation took place in 1925 and involved repeated honking of a car horn. Since then, similar studies have been conducted with electric toothbrushes and door buzzers, as well as the vibroacoustic stimulator.

In this study, fetuses were exposed to the vibroacoustic stimulation at 30, 32, 34, 36 and 38 weeks' gestation.

Fetuses as young as 30 weeks demonstrated a short-term memory of 10 minutes, and fetuses at 34 weeks seemed able to remember information they stored four weeks prior, the authors stated.

The level of stimulation the fetuses in this study received appears relatively high, another expert stated.

"I'm almost certain the baby heard it quite clearly and it was probably pretty loud," said Dr. Richard O. Jones, an assistant professor of obstetrics and gynecology at Texas A&M Health Science Center College of Medicine and medical director of obstetrics at Scott & White. "I almost wish I could do an ultrasound looking at the baby while they were making these loud noises. I would not be at all surprised to see the baby putting its hands over its ears."

And, of course, doctors routinely used different forms of stimulation to make sure a baby is alive and, literally, "kicking" while still in the womb.

"One of the things we do to monitor the health of a pregnancy is to have the mother count the baby's kicks. We like to see 10 movements in a two-hour period and most moms get 10 movements in about 20 minutes, especially if they time it after dinner," Jones said.

After reading this study, he added, if a mother complains that her baby isn't moving enough, one of the things he might suggest is turning the volume down.

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